1 Field of the Invention
The present invention relates to refrigeration systems with a condenser bypass valve and a hot gas bypass valve, which system finds particular but not exclusive utility in connection with a refrigerated gas separation apparatus and, more particularly, refrigerated dryers and separators for removing moisture from compressed air.
2 Prior Art
Refrigerated dryers and moisture separators for removing moisture from compressed air are generally old and well-known in the art. Such apparatus conventionally includes a conditioner or equalizer in the form of a shell and tube heat exchanger for cooling incoming hot, moist compressed air and warming outgoing cold, dried compressed air. The cooled, moist compressed air is then contacted with a refrigeration evaporator which further lowers the temperature of the compressed air, thereby causing moisture to condense for removal in a separator. Condensed moisture is removed and the cold, relatively drier compressed air is directed through the equalizer heat exchanger to cool incoming hot, moist compressed air before being discharged to the utility circuit.
The refrigeration evaporator is part of a conventional refrigeration circuit, including a refrigerant compressor, condenser, refrigerant reservoir, expansion valve or orifice, and evaporator.
A refrigerating system having a remote condenser subject to low ambient temperatures is shown and described in previously filed application Ser. No. 376,921, filed May 10, 1982, now abandoned. The disclosure of said application Ser. No. 376,921 is incorporated by reference herein and made a part hereof.
The refrigeration circuit shown in application Ser. No. 376,921 is an electromechanical refrigerating system which includes a receiver located close to the compressor and also as close to the evaporator as possible. The receiver acts as a reservoir with a volume capacity corresponding to that of both the evaporator and condenser. During periods of low condenser ambient temperature, the refrigerant liquefies near the start of the condenser coil and the condenser is full of liquid refrigerant. During periods of high condenser ambient temperature, the refrigerant does not cool and liquefy until near the end of the condenser coil and, because the gaseous refrigerant occupies a much greater volume than the liquid refrigerant, a reservoir such as the receiver is required for the remaining refrigerant.
When the condenser ambient temperature is very low, with correspondingly low refrigerant temperatures, the pressure and temperature drop across the thermostatic expansion valve are too low for effective operation of that valve. This problem is overcome with a condenser bypass valve which directs hot gaseous refrigerant directly into the receiver from the compressor, bypassing the condenser in the event the pressure of the liquid from the condenser falls below a predetermined level, as measured by the pressure differential between the gaseous compressor refrigerant and the liquid condenser refrigerant. The hot gaseous refrigerant discharged from the condenser bypass valve into the receiver quickly raises the temperature of the receiver refrigerant before it is routed to the thermostatic expansion valve.
Such a system is particularly useful during initial start-up under cold temperature conditions. The condenser bypass valve gradually throttles down the hot gas bypass as the evaporator adds heat to the system. Eventually, the condenser and other components approach normal operating temperatures and pressures, and no hot gas bypass is required.